Brake construction



Feb. 1, 1938. B. A. swENNEs BRAKE CONSTRUCTION Fild Aug. 26, 1936 riesigem?. 1, 193s i .y I' I A 2,107,092

BRAKE ooNs'raUc'noN l A. Swennes. Rockford,- lll.,' assignor to Borg-Warner Corporation, Chicago,- Ill., a corporation of Illinois v Application August 26, 193i, Serial No. 97,934 3 Claims. '(Cl; 18S-152) 'Ihis invention has to do with brakes for wheels A reservoir I 6 provided with a suitable air vent and more particularly with brakes of the servo and ller cap I'I supplies-liquid to the cylinderi type.v l through a tube I8 and a port I9, so located as to It is an object of the invention lto'provide a allow escape of liquid frorn'the cylinder `in rebrake construction embodying the advantages of sponse to expansion of the liq d and to permit 5` hydraulic and servo operation.A I A liquid to enter the cylinder w en the amount of It is another object of the invention to provide liquid in? the cylinder has .been depleted due to a servo brake so constructed as to' require a relacontraction and other causes. tively light initiating force. The inner part of the reduced cylinder portion l0 It is also an object of the invention to provide a I3 terminates in an enlarged cylinder portion 20 10 servo lbraise methanism including primary and in which is disposed ai. piston 2i provided with'a secondary shoes with means whereby movement leather or other suitable packing cup 22. A comof the primary shoe is transmitted in a multiplied pression spring .23 urges the pistons Il and 2l degree'to the secondary shoe. apart, the ends of the springs being received in A It is also an object of the invention-toprovide the cups I2 and 22, respectively. At any suitable 15 in. a servo brake a thrust transmitting member point uppermost in the'cylinder It, such as at the operative to adjust the shoes relative to the brake juncture. of the portions it and 2U, a bleederfurufrjso STATES v-P'rlavzN'r oFFlcfE surface. I l opening 24, suitably controlled as'by a plug (not im'ther objects and advantages of the inv'enshown) is located. j 29 Ation will appear as the description proceeds. A primary 5h06 2@ rries brake lining 2l )for 20 lThe invention will be best understood by refengagement with the brake surface of the drum erence to the following description of an `embod- 2 and 1S piOViiied with a t0@ 28 Urged against the iment thereof shown in the accompanying drawbearing plate 2S carried by the vpiston Thev ing, wherein: I v I toe 281s illustrated in its oli position, where Fig. l. is a section-elevation view of the invenittisurgedgby a returnspring 3u connected to the 25 tion. shoe and to the mounting plate i. To preventthe I rig. 2 is an enlarged fragmentary section-elepressure of the spring 3@ from building 11p presvation taken substantially as indicated -by the sui-e of fluid between the packing cups l2 and. line ,EI-E in Fig. i. 22and hence to avert deterioration of the cups,

3o Fig. 3 shows details of construction, taken suba'stop plate 3l is secured to the free end of the 30l l stantially as indicated by the une III- m in Fig. enlarged cylinder portion 2@ and provides a stop 1, biit for convenience turned clockwise 96. against which shoulders onI the toe it abut as In Fig. l therey is shown brake shoe supporting clearly shown in Fig. 1. A dust-proof joint loe- I means such as a mounting or backing plate I tween the cylinder enlargement 20 and the toe 2 adapted to be fastened to the axle or axle housing is effected by a boot @2.o 35

and in cooperative relation with @brake drum' 2 I The shoe 2G is provided with a guide spring or providing a brake surface for engagement with clip 33 to cooperate with other means, such as the i relatively movable brake means mounted on the mounting plate l, to assist in constraining th plate. Mounted on the plate I is a bracket 3 afshoe to substantially planar movement. l 'Y so fording a guide fora brake operating cable E, the The heel 3d of the shoe 2-6 is provided witha 4@ end ci which has a universal connection with an bracket 35 'which is pivoted at 36 to a fork or arm dof a lever t pivoted at 1 to a bracket 8 clevis 3l having a threaded'stem 33 threaded inmounted on the platei. Y y l to a turn buckle 3S provided with a 'wrench hold an intermediate potion of the lever 6 is piv.- or star Ml. The turnbuckle 39 is voppositely'inotallyconnected at d to a push rod I0 .having a. ternally threaded so as to receive the stem 38 and 45 preferably universal ball and socket-engagement the oppositely threaded stem 4I of a clevis 42 'with a piston il provided with a packing cup I2, pivoted at 43 to an intermediate portion offan slidaole in the reduced portion I-S of a combined arm or link M, one end of which is pivotallyan- .master and secondary cylinder I6 mounted on chored by a pin d5 to the mounting or backing 5o the plate I. The packing cup may -be of leather, plate I.. Y 1

/leather composition or other suitable material. A The pivot pin d5 is anchored in a reinforcing rubber or other preferably resilient boot I5 forms block 4 6 secured to the plate and is provided Awith a duid-tight joint between the reduced cylinder a- .shoulder 47 -betweenwhich and a' washer-48 portion it and the push-'rod I0, while permitting the arm' M is received. Axial movement of the. relative movement therebetween.

arm on the pin iswprevented' by a :retaining c '55 spring 49 snapped into a groove in the pin 45. A brake shoe return spring 50 is secured to the bracket 35 on the shoe 26 and to an ear on :the

washer 48, and is adapted to t between adjacent teeth of the star '40 on the turnbuckle 39 to prevent accidental change in adjustment of the turnbuckle. v

The pivot pin is cut to provide flats forming a wrench' hold 5I. 1

The arm 44 at its other end is straddled by a pair of rollers 52 adapted to engage the biglit 53 of a fork 54 extending free on the bracket 55 se-` cured to a secondary brake shoe 56 provided with brake lining 51. A 'spring 56 connected to an ear on the washer 49 and to the secondary shoe constantly urges said shoe to the "oif or. released position, and accordingly urges the bight 53 into engagement .with the rollers 52 carried by the arm 44.

A guidev spring or clip 33 attached to the shoe 56 cooperates with the mounting plate I or other suitable structure, to constrain the shoe 56 to movement substantially in a single plane.

The shoe 56 is pivotally anchored' at its other end 59 to a pin 69 which may be similar to the pin 45, and is retained by a C spring vlil similarA to the spring 49 hereinbefore referred to.

From the foregoing, it will be observed that when it is desired to apply the brake, means under the control of the driver, or, if desired, automatically operable, exerts a pull on the cable 4 in the direction indicated byrthe arrow 62,

causing they-push rod l0 to'thrust the piston il to the right as seen in Fig. 1. This pressure is transmitted inl an increased degree, due to the` a combined: radial and circumferential path.; K This movement of theshoe' 26 brings the lining 21`thereof-into engagement with the friction surface of thedrum 2, and as the latter rotates, it

'moves the shoe'V 26 in a direction toward the secondary Ishoe 56. This movement ofthe shoe 26 causes the clevis 31 and turnbuckle 39 to thrust the clevis 42 against the arm 44, turning the latter clockwise about the anchor pin 45 so as to force the rollers 42 against the bight 53 of thebracket 55. 'The swinging of the arm 45 causes the rollers 52 to move the secondary-shoe 56 outwardly about the pivot pin 60, where the shoe is anchored to the relatively stationary plate i, the lining 51 of said shoe being thereby forcibly engaged with the friction surface of the rotating drum 2.V

It?. will be appreciated that a relatively slight pressure of the push rod i0 on the piston Il is necessary to bring the primary shoe 26 into engagement with the drum. 2. Thereafter, the drum itself, due to its relative rotation, iseifective to cause both primary and secondary shoeslto more i As the drum initially turns I tightly grip the same. the shoe 26, forcing the lining 51 initially into engagementvwith vthe drum, saidshoe 56 offers greater resistance to its movement by the shoe.

26, which is thereby caused to grip the drum more tightly, resulting in vgreater pressure of the secondary shoe 56 against the drum, and this action continues asis well understood by those skilled in the g'rip between the shoes and the drum, returnfing the shoes to release or "off positions as shown in Fig. 1.

. The pivot 43 isdsubstannany closer to the-axis f of the pivot pin 45 than is any portion of the bight adapted to be engaged by the rollers 52.l -Accordingly a. relatively slight movement of the'clevis 42" in the direction of the arm 44,'due to a corre-y spondingly slight rotation of the primary -shoe 26 by the piston 2i and drum 2, will result in a substantially increased degree of movement of the secondary shoe 56 toward the friction surface of the 'drum 2.

It will be observed that the invention is .of such vcharacter as to adapt it 'to conventionalvmotor vehicles since the employment of the 'combination hydraulic and mechanical means requires lever 6 and bracket 8 are of a character to-be fou-nd'on present day installations of the mechanical type, and this is also 4substantially true ofthe push rod ID.

no reorganizationof brake linkage. Thecable 4,

It is also to be noted that the resistance offered 4 by thearm 44 and 'shoe 5a to'theturning of the primary shoe 26- is exerted in .such a vpath ,as to cause Ithe outer end 'of the 'turnbuckle link to Swing outwardly so as to swing the Iheel 34 of the shoe 26 outwardly in a direction tending to wedge theshoe 26 against the drum 2, which then increases the thrust on the arm `and secondary shoe, producing a servo actionji I am aware that many changes may be made and numerous detailsv of construction may be varied through ahwide range without departing from the principles of this invention, and I therefore `do not purpose limitingv the patent granted hereon otherwise than `by the appended claims I claim as my/invention:

ment of said shoe by said drum, a secondary shoe, Y. a forked extension on said secondary shoe, a pivoted lever mounted on said plate, rollers on the free end of said lever, and a link" connecting said f primaryV brake shoe to a point on said lever intermediate the rollers and pivot thereof, whereby a 1. In a servo brake, a brake drum, a plate, a, primary brake shoe,.rneans for initiating engage-v chang in the spacing between said primary'and secondary brake shoe as a result of the application of brakingpressure is eifectuated by a shift mary brake shoe, and means on said plate for initiating engagement vof said shoe by said drum, said means comprising a pair of cylinders having a fcommunicating passage therebetween, one of said cylinders being of greater diameter than the oth# er, pistons in each cylinder, external mechanical; control means for actuating the smaller piston, a bearing surface on the open end of the llarger piston and adapted to bear against one end of v said -primary brake shoe,'fiuid intermediate said pistons, a p'ort for admitting said iiuid into onejof the cylinders, and compressible means tending to said pist ns and bearing upon-adjacent surfacesl l .thereoi BENJAMIN A. 

